As high performance of an electronic component has been advanced in recent years, a semiconductor device on which the electronic component is highly integrated has been developed. As such a semiconductor device, for example, an electronic-component embedded substrate which is three-dimensionally mounted is known, in which the electronic component is mounted on a wiring substrate, another wiring substrate is stacked on the wiring substrate, and they are sealed by a resin, as described in Japanese Patent Application Laid-Open Publication No. 2008-153492 (Patent Document 1).
As illustrated in FIG. 11, in an electronic-component embedded substrate 48 described in Patent Document 1, an electronic component 30 is mounted on an upper surface of a lower-layer side wiring substrate 10 between two substrates of the lower-layer side wiring substrate 10 and an upper-layer side wiring substrate 20, and the lower-layer side wiring substrate 10 being a first wiring substrate and the upper-layer side wiring substrate 20 being a second wiring substrate are electrically connected with each other by solder balls 40. Also, a sealing resin 45 is injected between the lower-layer side wiring substrate 10 and the upper-layer side wiring substrate 20 so as to cover the electronic component 30. A bonding pad 12 formed on the lower-layer side wiring substrate 10 and an electrode 32 formed on the electronic component are electrically connected with each other by a bonding wire 46, and a resin 47 is coated on a bonding portion between the electrode 32 and the bonding wire 46.
Further, bumps 14 each made of solder or others are bonded on a lower surface of the lower-layer side wiring substrate 10. On the other hand, circuit components 16 such as a capacitor, a resistor, and an inductor and the electronic component 30 are mounted on the upper surface of the lower-layer side wiring substrate 10. Note that wirings and electrodes formed on an upper surface and a rear surface of each of the lower-layer side wiring substrate 10 and the upper-layer side wiring substrate 20 in FIG. 11 are not illustrated.
Still further, FIG. 12 is a plan view partially illustrating the electronic-component embedded substrate 48 illustrated in FIG. 11. Note that, in order to easily understand the structure in FIG. 12, only the lower-layer side wiring substrate 10, the electronic component 30 arranged on the upper surface of the lower-layer side wiring substrate 10, the circuit components 16, and the solder balls 40 are illustrated. And, the upper-layer side wiring substrate 20, the sealing resin 45, the bonding wire 46, the resin 47, and wirings on the upper surface of the lower-layer side wiring substrate 10 are not illustrated.
In the electronic-component embedded substrate 48, as illustrated in FIG. 11, wiring electrodes (not illustrated) formed on respective surfaces of the lower-layer side wiring substrate 10 and the upper-layer side wiring substrate 20 are electrically connected with each other by the solder ball 40. The solder ball 40 is formed by coating an outer surface of a Cu core 42 made of Cu (copper) in a spherical shape by solder 44. The solder ball 40 including the Cu core 42 has a function of a spacer between the lower-layer side wiring substrate 10 and the upper-layer side wiring substrate 20 so that the electronic component 30 mounted on the lower-layer side wiring substrate 10 does not contact the upper-layer side wiring substrate 20. Therefore, it is required that a diameter of the solder ball 40 is larger than a height from the upper surface of the lower-layer side wiring substrate 10 to an upper surface of the electronic component 30 when the electronic component 30 is mounted.
Such a structure that, the plurality of wiring substrates each mounting the electronic component are stacked, the wiring of each wiring substrate is electrically connected with the other, and the entire of them is sealed by the resin, is generally called “PoP (package on package)” because another package is stacked on a package. The package in which the electronic component is highly integrated by the PoP structure is used for a semiconductor device for communication which mounts a plurality of electronic components such as a high-frequency power amplifier, a surface acoustic wave filter, or an antenna switch, or a semiconductor device called “SiP (system in package)” which mounts a plurality of DRAMs (dynamic random access memory) or microcomputers. Also, the semiconductor device is used in mobile equipment such as a mobile phone and a digital still camera, and a consumer product such as a digital television and a laser beam printer.